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We studied the effect of different concentration of streptomycin in growth of Mycobacterium Tuberculosis strains. The results showed that in Streptomycin resistant and sensitive strains addition of 0.1 µg/ml and 0.01 µg/ml of Streptomycin in Lowenstein media, enhanced the appearance of colony about 5-7 and 1-5 days respectively. This observation may be due to the effect of Streptomycin on porin proteins of Mycobacterium Tuberculosis cell wall. Strains of M.tub showed modified colony morphology in the presence of low concentration of Streptomycin (0.1 & 0.01 µg/ml).